1. Field of the Invention
The present invention relates to a composite casing structure, and more particularly to a composite casing structure applied to a housing of an electronic device.
2. Related Art
A chassis of an ordinary notebook computer is usually divided into four parts. The first part refers to an outer cover of a liquid crystal display (LCD) (LCD Rear Cabinet, commonly referred to as Part A in the industry); the second part refers to a frame of the LCD (LCD Front Cabinet, commonly referred to as Part B in the industry); the third part refers to a keyboard frame (Top Cabinet, commonly referred to as Part C in the industry); and the fourth part refers to a base of the notebook computer (Bottom Cabinet, commonly referred to as Part D in the industry).
In addition, notebook computers are divided into two usage types, that is, commercial notebook computers, and notebook computers for industrial or military purposes. Therefore, it should be noted that the requirements of notebook computers for industrial or military purposes are different from those of commercial notebook computers when designing the notebook computers for industrial or military purposes. The notebook computers for industrial or military purposes are always used in harsh environments, for example, operated in excessively humid or dusty environments, so that the notebook computers for industrial or military purposes have much higher requirements for water proof, dust proof, and impact resistance than the commercial notebook computers. That is to say, when a notebook computer for industrial or military purposes is designed, the strength of a housing structure thereof should be considered first, and the waterproof or dustproof function must be considered at the same time.
Therefore, currently, the design of notebook computers for industrial or military purposes by various manufacturers all actively develops toward thin structure, light weight, and high structural strength. Hence, lightweight materials, such as a carbon fiber material, a magnesium alloy material, and a plastic material, are usually used as raw materials for manufacturing a chassis, and parts of the chassis are designed by using the above materials in combination, and the characteristics of the selected materials directly influence the structural strength of the chassis of the notebook computer.
For example, if an outer cover (i.e., Part A) of the chassis is made of a plastic material, although the chassis weight of the notebook computer can be greatly reduced, the plastic chassis is easily cracked or even directly broken due to insufficient rigidity of the plastic material when a strong external force impacts the plastic chassis. Further, as notebook computers for industrial or military purposes are gradually developed toward compact size, the main board and electronic elements therein all require precise mechanism design. If the chassis is made of the plastic material, operation elements in the notebook computer are more easily damaged under impact due to insufficient strength. Moreover, since the plastic chassis also has many other problems such as poor heat dissipation and difficulty in recovery, treatment and recycling, the plastic chassis will be phased out in the market.
Therefore, in order to meet the requirements for lightweight and high-strength structure of notebook computers for industrial or military purposes as well as the environmental protection concept of recovery and recycling, relevant manufacturers use an aluminum-magnesium (AlMg) alloy material to manufacture chassis of notebook computers. The advantages of AlMg alloy include high strength hardness and light weight. However, due to high chemical activity, the AlMg alloy has low corrosion resistance, such that the AlMg alloy housing cannot easily achieve some special test specifications. For example, formation of hair lines on the surface of the AlMg alloy housing by anodic treatment cannot be easily achieved by the AlMg alloy housing. Moreover, the high fabrication cost of the AlMg alloy keeps the unit price of the AlMg alloy housing high.
In addition, when fabricating an outer cover (i.e., Part A) of a chassis, a stud is usually disposed on an edge surface of the outer cover, and a circuit board is disposed and positioned on the stud, so that a perforation on the circuit board is aligned with a screw hole of the stud. Afterwards, a frame of an LCD (i.e., Part B) and the outer cover are assembled to each other so that a screw hole of the frame is corresponding to the perforation of the circuit board and the screw hole of the stud. Then, a fastening element is passed through the screw hole of the frame and the perforation of the circuit board, and fastened in the screw hole of the stud, so that the circuit board can be tightly fastened between the outer cover and the frame.
However, due to light weight and thinness of the AlMg outer cover, if the AlMg outer cover itself is stamped or forged to form a specific structure (for example, a stud) by mechanical processing, the AlMg outer cover is easily broken or damaged due to an excessively large processing force. If a stud is fixed on the AlMg outer cover by welding or adhesion after the AlMg outer cover is formed, the entire fabrication process has to be performed by stages, which consumes much labor time and increases the fabrication cost. Moreover, the welding or adhesion manner easily damages the surface of the AlMg outer cover and impairs the appearance, and also easily causes the problem of flatness when studs are fixed on the AlMg outer cover.
Therefore, how to fabricate an outer cover (i.e., Part A) of a chassis which has a high-strength and lightweight structure as well as a complex structural design and facilitate various processing treatment (for example, chemical treatment such as anodic treatment) while reducing the fabrication cost is a problem to be solved by persons involved in the industry.